1. Field of the Invention
The present invention relates to the protective coating of articles and, more particularly, to a protective lubricant for metal bodies made of titanium and titanium alloys.
2. Description of the Prior Art
It is necessary to protectively coat titanium articles to lubricate surfaces subject to bearing or friction forces. Furthermore, titanium surfaces in contact at room temperature must be prevented from cold welding. Improved coating materials are needed since titanium is being considered increasingly for applications in the aircraft, aerospace, automotive and marine fields.
Titanium has been protectively coated by anodizing treatments, graphite containing coatings, molybdenum sulfide coatings in various vehicles and tallow. These treatments have not been satisfactory under various conditions of service and have been found to interfere with subsequent fabrication techniques. During fabrication, the coating must withstand temperatures of 500.degree. F or more during welding or bending operations. The coating must be coherent and adherent to the surface so that it can withstand abrasion forces encountered during handling, fabrication and service.
The coatings prior to this invention have been found to vaporize and fume in high temperature environments and to lose their effectiveness in short periods of service by running off the surface in liquid form or abrading from the surface in objectionable dust form. Furthermore, welding was impractical unless special joining procedures were practiced. Also, the surface appearance was unattractive due to staining and wetting. Moreover, a protective coating was difficult to apply without changing the dimensional tolerances of metal articles.